Interlude: Basic anatomy of larval dragonflies
From the pictures on the previous page, it is clear that dragonfly larvae can come in many shapes, and this variation is important in identification. To aid this process it is necessary to provide an overview of larval anatomy – with a focus on the features used to distinguish among families and species.
The diagrams below illustrate the important features of larval dragonflies used in this guide. All insects are divided into three body regions: 1) head, 2) thorax, and 3) abdomen, and features found on the head and abdomen are of particular usefulness in identifying exuviae. On the head, pay attention to the shape of the Acadia Learning field guide to dragonfly larva Interlude: Basic anatomy of larval dragonflies ANTENNAE and of the LABIUM. The labium is an extendable “lower lip” that is used to catch prey. It can be eitherFrom a) the flat pictures or b) on scoop-shaped the previous page, when it is viewedclear that from dragonfly the larvaeside. Atcan thecome end in manyof the shapes, labium and are this a pair of PALPAL There are a lot of things to look at on a dragonfly body- familiarize yourself with some of the LOBESvariation that is important are folded in identification. together in Toexuviae. aid this processPay attention it is necessary to the to shape provide of an t heoverview BLADE, of larval including the size and body part names: numberanatomy of – TEETH.with a focus On on thethe featuresabdomen, used note to distinguish the overall among shape, families plus and the species. size and shape of DORSAL HOOKS and LATERAL SPINES. The diagrams below illustrate the important features of larval dragonflies used in this guide. All insects are divided into three body regions: 1) head, 2) thorax, and 3) abdomen, and features found on the head and Darnerabdomen larva are ofshowing particular basic usefulness body in areas: identifying exuviae. On the head, pay attention to the shape of the ANTENNAETibia of front and leg of the LABIUM. The lateral labium spines is an extendable “lower lip” that is used to catch prey. It can be either a) flat or b) scoop-shaped when viewed from the side. At the end of the labium are a pair of PALPAL LOBES that are folded together in exuviae. Pay attention to the shape of the BLADE, including the size and number of TEETH. On the abdomen, note the overall shape, plus the size and shape of DORSAL HOOKS and a. LATERAL SPINES.
Darner larva showing basic body areas: b. Tibia of front leg lateral spines
Head Thorax Abdomen antennae of clubtail showing wide third segment (compare to slender antennae on diagram to left)
c. Head Thorax palpal lobes Abdomen antennae of clubtail showing wide third segment (compare to slender antennae on diagram to left)
scoop-shaped labium flat labium (darner) close-up of palpal lobes showi ng teeth scoop-shaped labium flat labium (darner) close-up of palpal lobes showing teeth (skimmer) (skimmer) (clubtail) (clubtail) d. mentum
Mouthpart, also called the labium. The labium is made up of two big parts- the 2 mentum and the palpal lobes 2
a. from: A General Guide to Dragonfly Exuviae, Pamela Hunt, h p://www.wildlife.state.nh.us/Wildlife/Nongame/ dragonflies.html b. from: Soltesz, Ken. 1996. Iden fica on Key to Northeastern Anisopters Larvae, University of Connec cut, CT. www.odenews.org/NEAnisopteraSpeciesKey.pdf c. from: A General Guide to Dragonfly Exuviae, Pamela Hunt, h p://www.wildlife.state.nh.us/Wildlife/Nongame/ dragonflies.html d. from: A Genus Key to the Odonate Larvae of the Northeastern United States. 1998. Karen Frolich. Acadia Learning field guide to dragonfly larva These are photos of dragonfly exuvia (shells le behind when the dragonflies become adults), your dragonflies will look quite different Answer this: What’s the shape of the Family Aeshnidae: labium? Flat? large eyes Aeshnidae or Gomphidae long abdomen Spoon, or mask-like? flat labium Cordulegastridae, long thread-like Macromiidae, Corduliidae antennae (not or Libellullidae
shown) It’s got a flat labium… what about the eyes and antennae? Big eyes (rela vely speaking) and thread-like antennae? Family Gomphidae: Aeshnidae stubby antennae Small eyes and stubby antennae? smaller eyes Gomphidae flat labium Answer this: It’s got a mask-like labium… what about the palpal lobes? Family Cordulegastridae: Really jagged? usually stocky Cordulegastridae spoon or mask-like Not too jagged, or labium and the palpal look more like a lobes have very zipper? jagged edges Macromiidae, Corduliidae or Libellullidae
Does is have a horn? Macromiidae Family Macromiidae: o en flat and coin-shaped. No horn? spoon or mask-like labium Corduliidae or palpal lobes have very Libellullidae (these regular edges, and in two are very confusing) between the eyes there is a ‘horn’ (o en have very, very long legs)
Looking at the abdomen from the side… Families Cordulliidae and Are the things that s ck out spiky, Libellulidae (hard to tell rounded, not there? Libellulidae Hooked? Cordulliidae apart): Libellulidae They have the spoon-shaped In Libellulidae the anal pyramid (the very tail end) is long with three long points and two shorter spines. The anal pyramid in Corduliidae is generally short with all five labium, regular edges (also points of equal length. called crenella ons) on the Corduliidae palpal lobes but… All images on this page © 2011 Wilbur Anderson, Kingfisher Photography